When to plant Basil in Subtropical Australia

Subtropical zone — applies to Brisbane, Gold Coast, Sunshine Coast, Coffs Harbour, Lismore and similar areas. Growing elsewhere? Temperate · Cool · Tropical · Arid.

Sow basil direct from August through January in the subtropical zone, barely 3 mm deep, once nights are warm. Germination is quick at 7–14 days and plants hit full production in 60–90 days, though you can start pinching leaves well before that. Basil genuinely enjoys the subtropical summer — the warmth and moisture that hammer Mediterranean herbs suit it perfectly, and a single Brisbane sowing can carry a kitchen through to autumn. Space plants 25–40 cm apart in full or morning sun, and remember it is frost tender: the first cold snap of an inland winter ends the season.

Sowing calendar — subtropical zone

Green months are your sowing window: August to January.

Growing notes

Few herbs are as well matched to this climate. Sown in spring on the Gold Coast or around Lismore, basil romps through the humid months when parsley sulks and coriander bolts. The window closing at January is about the plant's lifespan rather than the weather — late sowings still crop, but shortening days push them to flower sooner, so the biggest, longest-lived bushes come from September and October sowings.

Pinch the growing tips relentlessly. Every pinch delays flowering, doubles the branching, and keeps leaves large and sweet; once flower spikes take over, flavour coarsens. Rich, moist soil, mulch, and steady water keep growth soft, and a follow-up sowing every four to six weeks guarantees supply if an older plant runs to seed.

The failure mode to know is downy mildew, which thrives in still, wet February air: leaves yellow between the veins with a grey-purple fuzz underneath, and it spreads fast. Use the full 40 cm spacing for airflow, water at the base in the morning, pick hard, and pull badly infected plants rather than nursing them — at 7–14 days to germinate, a replacement sowing catches up quickly. On the frost-free coast a few plants may limp through winter, but basil is best treated as an annual here.

Basil at a glance

Companion planting

Grows well with

Tomatoes: Repels aphids and tomato hornworm; may improve flavour

Tomatoes: Repels aphids, thrips; may improve tomato yield

Marigold: Together a potent natural pest repellant

Common questions

When can I plant basil in Brisbane?

Sow direct from August through January. September and October sowings make the biggest plants, cropping right through summer and into autumn.

Why are my basil leaves yellow with grey fuzz underneath?

That is downy mildew, which flares in humid, still summer weather. Improve airflow with wider spacing, water at the base in the morning, and pull badly affected plants and resow.

How do I stop basil going to seed?

Pinch out the growing tips every week or two and remove flower spikes as soon as they appear. Sowing a fresh batch every four to six weeks keeps young plants coming as older ones bolt.

Will basil survive winter in the subtropics?

Sometimes on the frost-free coast, where plants limp through and pick up again in spring, but it is frost tender and any inland frost kills it. Most gardeners simply resow from August.

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